Idempotent characters and equivariantly multiplicative splittings of K-theory

We classify the primitive idempotents of the $p$-local complex representation ring of a finite group $G$ in terms of the cyclic subgroups of order prime to $p$ and show that they all come from idempotents of the Burnside ring. Our results hold without adjoining roots of unity or inverting the order of $G$, thus extending classical structure theorems. We then derive explicit group-theoretic obstructions for tensor induction to be compatible with the resulting idempotent splitting of the representation ring Mackey functor. Our main motivation is an application in homotopy theory: we conclude that the idempotent summands of $G$-equivariant topological $K$-theory and the corresponding summands of the $G$-equivariant sphere spectrum admit exactly the same flavors of equivariant commutative ring structures, made precise in terms of Hill-Hopkins-Ravenel norm maps. This paper is a sequel to the author's earlier work on multiplicative induction for the Burnside ring and the sphere spectrum, see arXiv:1802.01938.Comment: 19 pages. Comments welcome! v2: Updated references. Removed a lemma that is no longer relevant. v3: Changes in response to a referee repor

Monopolistic Location Choice in Two-Sided Industries

We analyze the optimal location choice of a monopolistic firm that operates two platforms on a two-sided market. We show that the optimal platform locations are equivalent to the one-sided benchmark if both sides are either restricted to single- or multi-homing. In the mixed case (one side single-homes, the other one multi-homes), the optimal platform locations are determined by the relative profitability of both market sides. Our results indicate that modeling mergers on two-sided markets with fixed locations is often inappropriate

Persistence of complex food webs in metacommunities

Metacommunity theory is considered a promising approach for explaining species diversity and food web complexity. Recently Pillai et al. proposed a simple modeling framework for the dynamics of food webs at the metacommunity level. Here, we employ this framework to compute general conditions for the persistence of complex food webs in metacommunities. The persistence conditions found depend on the connectivity of the resource patches and the structure of the assembled food web, thus linking the underlying spatial patch-network and the species interaction network. We find that the persistence of omnivores is more likely when it is feeding on (a) prey on low trophic levels, and (b) prey on similar trophic levels

A note on the relationship of mainstream and art house movie theaters

We use a set of German micro data to study the relationship between mainstream and art house movie theaters. We find that both types of cinema have a significant price effect within their own group, but there is no significant price effect between the two types. Furthermore, we provide an example for the biased results that occur, if both types of movie theaters are pooled into one regression. Doing so, we demonstrate that it is important, to carefully distinguish mainstream and art house facilities in empirical studies of the movie theater industry.substitutability; complementarity; movie theater industry; Germany

Searching for the Concentration-Price Effect in the German Movie Theater Industry

This paper investigates whether a price-concentration relationship can be found on local cinema markets in Germany. First, we test a model of monopolistic pricing using a new set of German micro data and find no significant difference in admission prices on monopoly and oligopoly markets. In a next step, we test whether this can be explained by the existence of local monopolies, but find no hint of that. Implicit or explicit collusion among cinema operators might explain our observations.price-concentration study; cinema pricing

A note on the relationship of mainstream and art house movie theaters

We use a set of German micro data to study the relationship between mainstream and art house movie theaters. We find that both types of cinema have a significant price effect within their own group, but there is no significant price effect between the two types. Furthermore, we provide an example for the biased results that occur, if both types of movie theaters are pooled into one regression. Doing so, we demonstrate that it is important, to carefully distinguish mainstream and art house facilities in empirical studies of the movie theater industry.substitutability; complementarity; movie theater industry; Germany

Is the Informal Sector Constrained from the Demand Side? Evidence for Six West African Capitals

Employing a unique dataset that covers households from six West African capitals, this paper provides new evidence on the demand for informal sector products and services. We first investigate whether demand linkages exist between formal and informal products and distribution channels, and whether there is an overlapping customer base, which would imply that both formal sector wage earners and informal workers buy both formal and informal products using both formal and informal distribution channels. In a second step, we estimate demand elasticities based on Engel curves. We find a strongly overlapping customer base and strong demand-side linkages between the formal and informal sector, with the exception that informal goods are hardly bought through formal distribution channels. The estimated demand elasticities tend to show that rising incomes are associated with a lower propensity to consume informal sector goods and to use informal distribution channels. We therefore conclude that the informal sector in West Africa is likely to be constrained from the demand side. --Informal sector,formal-informal linkages,Engel curve estimates,West Africa